Anya Plutynski

Natural selection is an extremely powerful process – so powerful, in fact, that it is often tempting to deploy it in explaining phenomena as wide-ranging as the persistence of blue eyes, the origins or persistence of religious belief, or, the history of science. One long-standing debate among both critics and advocates of Darwin’s concerns the scope of Darwinian explanations, and how we are to draw the line. Peter Godfrey-Smith’s Darwinian Populations and Natural Selection is a detailed examination of this question. The book explores the criteria for what may count as a “Darwinian population,” by which Godfrey-Smith means, which collections of entities have the capacity to undergo evolution via natural selection (p. 6). Drawing upon his answer to this question, Godfrey-Smith examines and provides his own solution to the following long-standing debates in philosophy of biology: (a) the twin problems of reproduction and individuation of biological entities, (b) the persistent “gene’s eye view,” (c) the levels and units of selection problem, and (d) the evolution of cultural artifacts and behaviors.

There have been two different schools of thought on the evolution of dominance. On the one hand, followers of Wright [Wright S. 1929. Am. Nat. 63: 274–279, Evolution: Selected Papers by Sewall Wright, University of Chicago Press, Chicago; 1934. Am. Nat. 68: 25–53, Evolution: Selected Papers by Sewall Wright, University of Chicago Press, Chicago; Haldane J.B.S. 1930. Am. Nat. 64: 87–90; 1939. J. Genet. 37: 365–374; Kacser H. and Burns J.A. 1981. Genetics 97: 639–666] have defended the view that dominance is a product of non-linearities in gene expression. On the other hand, followers of Fisher [Fisher R.A. 1928a. Am. Nat. 62: 15–126; 1928b. Am. Nat. 62: 571–574; Bürger R. 1983a. Math. Biosci. 67: 125–143; 1983b. J. Math. Biol. 16: 269–280; Wagner G. and Burger R. 1985. J. Theor. Biol. 113: 475–500; Mayo O. and Reinhard B. 1997. Biol. Rev. 72: 97–110] have argued that dominance evolved via selection on modifier genes. Some have called these “physiological” versus “selectionist,” or more recently [Falk R. 2001. Biol. Philos. 16: 285–323], “functional,” versus “structural” explanations of dominance. This paper argues, however, that one need not treat these explanations as exclusive. While one can disagree about the most likely evolutionary explanation of dominance, as Wright and Fisher did, offering a “physiological” or developmental explanation of dominance does not render dominance “epiphenomenal,” nor show that evolutionary considerations are irrelevant to the maintenance of dominance, as some [Kacser H. and Burns J.A. 1981. Genetics 97: 639–666] have argued. Recent work [Gilchrist M.A. and Nijhout H.F. 2001. Genetics 159: 423–432] illustrates how biological explanation is a multi-level task, requiring both a “top-down” approach to understanding how a pattern of inheritance or trait might be maintained in populations, as well as “bottom-up” modeling of the dynamics of gene expression.

Mainstream philosophy of science has embraced an “empiricist” approach to scientific method. To be slightly more precise, I venture that most philosophers of science today would endorse the view that experience is the source of most scientific knowledge. The aim of this essay will be to challenge the consensus, by showing how we cannot and should not abandon all elements of the “rationalist” tradition, a tradition often identified with philosophers such as Descartes. There are several elements frequently identified with “rationalist” science (Stump, 2005): questioning of sense experience, the attempt to rethink the “metaphysical” foundations of one’s science, using either thought experiment, or appealing to demonstrative arguments purporting to establish ‘necessary’ truths, often using either mathematics or geometry, and appeal to “virtues” not usually considered “strictly empirical,” such as simplicity. This essay explores the effective deployment of such considerations in the history and current practice of science.

Roderic Page’s new book, Tangled Trees: Phylogeny, Cospeciation and Coevolution (2003), is a worthwhile read for anyone interested in either methodological issues in systematics, or how organisms shape one another’s selective environments. “Cospeciation,” for the uninitiated, is the concurrent speciation of two or more lineages that are ecologically associated (e.g. host-parasite associations, as well as mutualistic or symbiotic associations). “Coevolution,” in contrast, is the reciprocal adaptation of hosts and parasite taxa. The main focus of Page’s book is thus when, how and why the branching process of host taxa mirrors that of parasite taxa. “Parasite” here is broadly conceived to be anything from a louse to a virus to a retrotransposon, and “host” may be anything from a genome to a whale.

This paper uses a number of examples of diverse types and functions of models in evolutionary biology to argue that the demarcation between theory and practice, or “theory model” and “data model,” is often difficult to make. It is shown how both mathematical and laboratory models function as plausibility arguments, existence proofs, and refutations in the investigation of questions about the pattern and process of evolutionary history. I consider the consequences of this for the semantic approach to theories and theory confirmation. The paper attempts to reconcile the insights of both critics and advocates of the semantic approach to theories.